The purpose of this project is to apply digital subtraction angiography to the measurement of coronary artery blood flow and myocardial perfusion. The objectives are to: (1) measure coronary artery blood flow accurately and reproducibly, (2) determine the physiological importance of coronary artery obstructive disease by measuring flow and perfusion during basal conditions and reactive hyperemia, (3) measure the area and pattern of myocardial perfusion in areas of myocardium supplied by normal and partially obstructed coronary arteries, and (4) measure myocardial perfusion characteristics of areas supplied solely by collateral blood flow. Currently, the anatomical constriction in a coronary artery as determined by coronary angiography is the major indication for operative intervention. The long-term goal of these studies is to quantitate the physiological importance of the obstruction so that corrective measures can be taken only when the disease is of physiological importance. These methods may also be used to assess the results of balloon dilatation or streptokinase infusion immediately in the catheterization laboratory. Coronary artery flow will be measured by cross-correlation transit-time techniques and compared to electromagnetic flowmeter measurements. The hyperemic response to paired contrast injections and adenosine infusion will be compared to the hyperemic response following a 20-second arterial occlusion in both perfusion and flow studies. Myocardial perfusion using videodensitometry will be studied in normal arteries, arteries partially stenosed by a constrictor, and arteries totally occluded by a constrictor receiving flow totally through collaterals. Qualitative estimates of areas of perfusion measured angiographically will be compared to quantitative estimates using radioactive microspheres. In addition, patterns of perfusion will be evaluated by wash-in and wash-out curves. The implementation of these techniques through a readily available general purpose image-processing computer and digital subtraction angiography should allow for widespread acceptance.